An explosion on the second floor of the Heritage Inn, located on Channel Way near Sports Arena Boulevard, caused an estimated $600,000 in damage to the hotel and injured three of the hotel’s guests on Jan. 30, according to authorities.

Just after 11 a.m., several people from the hotel called 911, saying they heard an explosion, people screaming and saw flames emitting from the building. Once fire crews arrived on scene, the blaze was extinguished within minutes, said San Diego fire department spokesman Maurice Luque.

According to police reports, a 21-year-old man and a woman in her 20s were extracting hash oil from marijuana using spray cans of butane when the man lit a cigarette and ignited the butane fumes.

“This is the first explosion we’ve had from [a hash oil extraction lab] in San Diego County,” said Amy Roderick, Drug Enforcement Administration (DEA) spokeswoman. “A lot of times they sell that to dispensaries because the dispensaries use the hash oil in a lot of the edibles.”

The man suffered critical burns over his entire body and the woman suffered serious injuries to her face, hands and feet. Another hotel guest, a 20-year-old man in the adjacent room, had minor injuries to his face and hands from the blast.

“The heat of the blast ignited insulation in the blown-open walls and the fire traveled up through the walls into the attic,” said Luque of the extent of the hotel’s damage, which included $500,000 in damage to the structure and a $100,000 loss to contents in the rooms affected by the blast and fire.

All injured parties were transported to the UC San Diego Medical Regional Burn Center following the explosion, and the DEA is investigating the incident.